Project Summary Learning to avoid environmental threats is essential for survival. Our knowledge of the neural substrates within the central nervous system responsible for learning to avoid such threats is incomplete. The precise analysis of the function and regulation of specific neurons within neural circuits that mediate threat perception and avoidance is essential for our understanding of these basic neural processes and the etiology of neurological and psychiatric disease. We have identified a population of neurons within the parabrachial nucleus (PBN) that express calcitonin gene-related peptide (CGRP). This specific population of neurons is necessary and sufficient for mediating behavioral responses to foot shock and visceral malaise. Experimental activation of CGRP-neuron terminals in the central nucleus of the amygdala is sufficient to generate fear or taste memories; however, activation of CGRP receptor (CALCRL) neurons in the CeA is sufficient for fear conditioning but not for taste conditioning. This multi-investigator proposal will draw on the expertise of three PIs (Dr. Zweifel, Dr. Palmiter, and Dr. McKnight) to discover how different threats are differentially recognized by the central nucleus of the amygdala (CeA). To address this fundamental question we will integrate cutting-edge techniques in mouse genetics, viral-mediated circuit dissection, behavior, in vivo imaging, electrophysiology, and cell-specific molecular profiling. We will characterize the molecular profile (translated mRNAs) of postsynaptic CGRP receptor (CALCRL)-expressing and non-CALCRL expressing neurons in the CeA to establish the identity of these neurons recruited during conditioned taste aversion and fear. We will elucidate the extent of activation of these circuit components using in vivo calcium imaging of circuit dynamics in freely behaving mice. We will establish how distinct noxious stimuli associated with pain or visceral malaise diverge at the level of CALCRL-and non-CALCRL expressing neurons in the CeA through functional manipulation of these neural circuit connections with light- and drug-activated receptors. Successful completion of this proposal will delineate key circuit components underlying aversive processing in the brain and will serve as a gateway to future investigations into downstream circuit components critical for these processes.